The 2123XST has a terminal connection which you can either solder to or use a connector. Allied sells a number of different fan connector cords, some for less than $1. They are listed by manufacturer so they are not all in the same place. Just page through the fan section of the catalog.

Following is a crude chart giving you some idea of resistor values to achieve reduced voltage on the 2123XST fan if you want to run it at less than 120V. Sorry for the format mangling the forum does. The watt number tells you how much the resistor must be capable of dissipating. You can put resistors in series to spread out the dissapation if you want, such as three 300 ohm 1Watt resistors in series will give you 900 ohms and each resistor will only be dissipating 1/3 of the power which will be less than 1watt per resistor. The 2123XST will just barely start at 70V, not bad for a 230V fan.

To give you a point of reference on the 2123XST fan, the Line voltage here is around 125V (a bit higher than typical). For me 750 ohms gives me about 91 Volts on the fan and it runs about as quiet as a Nexus at 7V. 270 ohms gives me about 110V on the fan and it is roughly as noisy as a Nexus at 12V. 470 ohms gives me about 101 Volts on the fan and it's about as noisy as a Nexus at 9.5V and seems to be good noise vs airflow tradeoff point for me.

No offense princejoe, but how much hand-holding do you need? I mean, you find the site so that's good, your way ahead of a lot of other quiet PC cravers, but won't you take the time to read two pages of posts? I'll bold the "For you new guys having a hard time choosing" paragraph... I need to add ferdb's input anyway. By the way, I really doubt you will need more air then the Nexus's 12V CFM. Go for the Nexus unless you just simply can afford the extra cost over the Globes. Bear in mind though, you will need a fan controller for the Globe and you might not for the Nexus depending on what you feel is quiet. That said, the Zalman Fanmate is probably your cheapest best. Do a forum search on fan controllers before you one.

Has anyone had experience with the SilenX 120mm 14dBA (!) 1800rpm 58cfm fan? It's readily available in Canada at bigfootcomputers.com. I dropped in there and gave it a listen, just plugged right into a PSU and it was a lot quieter than the L120 Panaflo in my Sonata case - about the same at 12 v as the Panaflo is at 6 volt. Does anyone know if this fan is a rebadging of one of the above models? (They also have a slower model rated at 11 dba.) Mike C, I hope you can include these models in your upcoming roundup....

I got some of those overpriced Silenx 120's in. As pointed out before, the quoted noise specs on them are ludicrous. The Silenx running at 7v is about the same loudness as a 120 Nexus running at 12V. The Nexus flows more air under those conditions. The Airflow vs Noise ratio is worse than a Nexus but the CFM top end is much higher.You can however crank that Silenx up to 12V and it blows a lot of air.
It's not a bad 120 dc fan, sort of on a par with the Globe S1202512L-3M. The airflow vs noise ratio is very close to the Globe fan, but the Silenx has a bit of motor tick noise on top of it all and so loses out when you run the fans at lower rpm. The Silenx will run down to 3V.

The globe runs a bit faster at 12V than the Silenx, if you undervolt it till they are running at the same rpm they flow about the same air at about the same noise.
There is really no advantage of the Silenx over the Globe in any situation and it's much more expensive.
The Nexus is still the gold standard for 120mm DC fans.

Any thought MikeC on whether you could include ferdb's found AC fan in the 'big-honking' fan review? They appear to be very worthy of inclusion, despite being AC.

Yes I agree. I have used AC fans to cool radio gear and the ones I have used do seem to have a very good CFM/db ratio. There are also some fairly good temp speed controllers for AC fans that are available. In addition using an AC fan would reduce the load on the PSU a little so that should also run a little cooler. It would also be nice if recordings of some AC fans could be posted. I also think that there may be other AC fans out there that could be possible candidates for more testing. For example, Radio Shack sells 80mm, 92mm and 120mm AC fans. Easy to get and cheap. I have used the 120mm fan and it is rated at 80 CFM and is fairly quite.

i know nothing about fans, other then I want one that I will not be able to hear,

this is the system I intend to buy

if anyone is able to tell me which 120mm fan to buy and if possible will my current choice keep itself cool and will I be able to hear anything, and also if all the components will physicaly fit together, eg is there enough room to get the heatsink in, and get the 6800 ultra in.

The 2123XST has a terminal connection which you can either solder to or use a connector. Allied sells a number of different fan connector cords

I'm having trouble finding an image of that fan. Where do the connectors attach? In, next to the hub (where I'd sort-of expect). I'm thinking I'd probably need to stack a pair of these (with small plenum between) to get sufficient pressure for a 2" heater core at low noise levels - so this means I'd need the straight connectors, right? I'm also guessing from your post that the fan connector cords are interchangeable. Is that true or is there some particular kind I need to stick to. The Allied catalog assumes I have a background in whatever device I'm buying from them and already have this knowledge.

Re speed control. Any reason why a rheostat wouldn't work? These fans are rated for 22W at 220V - so 1 amp. Any reason why they'd draw more than that at 120V or 90? Or are they non-ohmic devices like processors?
Also, I have a couple of speed controllers for 115VAC fans from Edmund. I figure these are at least worth trying. Any reason they'd be a bad idea?

Finally - I'm pretty sure that the real answer to the noise/cooling trade off for 2" heater cores is to not use 2" heater cores. Nick over at Radiator Express has offered to make up a small radiator / heater core to my specs. I'm planning to ask for one that's 6x6x.5 (finned area). Should work nearly as well as the "old standby" - a chevette heater core as it's mostly frontal area that matters. Sorry for being off topic - except that sometimes the answer to a question is to change the question

About the CFM of the Nexus at 7 volts, is it REALLY that low? (Half the CFM of an 80L at 5v)?

I've got a relatively cool computer (2.6 P4, 9500 w/Silencer, Passive Northbridge, and 1 WD as my only heat producers), and pretty much everything is ducted out, as in my 2.6 is sucking heat right out of the case via duct, the Silencer is blowing the GPU heat right out the back, and my PSU is ducted (therefore its not sucking out any of the heat in the case).

With that setup and uncluttered airflow, would a 7V Nexus be alright? Or should I just stick with a 5V Globe??

About the CFM of the Nexus at 7 volts, is it REALLY that low? (Half the CFM of an 80L at 5v)?

The Nexus CFM at 7v is ~23-24CFM according to MikeC. I don't know here you're getting your CFM values for the 80mm L1A @5v from. Or are you refering to another fan?

ONEshot wrote:

With that setup and uncluttered airflow, would a 7V Nexus be alright? Or should I just stick with a 5V Globe??

I believe the correct assessment is the Nexus would be quieter than the Globe when both are run at the same RPM due to the Globe's bearing noise, so I would go for the Nexus as I doubt you are going to need more CFM than what the Nexus will give you at 12v (should [email protected] be insufficient).

bobkoure, let us know how those speed controllers from Edmund work out for you! Part of the difficulty with controlling AC fans is that they're speed is determined my the frequency, not just the current. That said, I don't see why you couldn't use a varible resistor as ferdb is using resistors to speed contol his AC Sunons.

As for the 2" heatercore, true, thinner rads are better for a quiet computing setup, but it's almost impossible to find a <2" rad that meets your max dimensions, and that isn't harmful to your liquid flowrates. Another issue is cost, though I'm sure many would be willing to pay a pretty penny to have a 1" thick heatercore/rad that fits their max dimensions and flow rates are not compromised. Personally, I plan on using the standard, cheap, 2" thick heatercores in my future setups and sandwiching them with the Sunons.

Another aspect I recently though of:

Heatercore thickness really wouldn’t be an issue if the surface area of the fins/grill was significantly larger than the sized fan used, right? I mean, and to use an extreme example, you're going to have a hard time convincing me that a Black Ice Pro (1" thickness, ~120x120mm grill) is going to be less restrictive than a Bonny core with a single shrouded 120mm on it (2” thickness, huge grill area)!

Let’s keep this thread closer to exclusively fan related though. I just posted this thought in <this> thread, so feel free to post comments concerning it there.

I got a PM from ferdb with regards to the Sunon and speed controlling. Posting with hopefully tacit permission. Once again, big thanks to ferdb!

ferdb wrote:

I've come up with an AC fan speed controller based off some cheap off the shelf parts that works well for the Sunon (but sadly not nearly as well for other AC fans I've tried). It uses a Lutron continously variable fan speed controller ($9 at Lowe's hardware) and a 4.7uF 250v capacitor. It does introduce a very slight 60hz hum in the fan, but it's pretty inaudible from 2 feet. Other fans that the Sunon tend to buzz and hum unacceptably, my off hand theory is that Sunon glued the motor laminations together and the other companies didn't. Anyway I'm getting to like these Sunons more and more. Other types of light dimmers and fan speed controls don't work well at all unfortunately, they tend to make a racket and work in fits and starts. The Lutron + Cap controller is smoothly variable from barely turning to quite a bit faster than regular 120V (the capacitor not only smooths out the hum and keeps the speed controller from freaking out, it also boosts the effective voltage on the fan up to 150-160vAC because the inductance of the fan and the cap resonate at around 60HZ. The cap also helps correct the power factor, which is probably of no practical value in this case. I just got some 120v pump relay PCI cards to turn my fans on and off so I need to start putting this whole system together and move my motherboard and drives out of this old Koolance chassis.I think my next project is going to be making an interface to allow me to control the AC fans with the T-Balancer.

The terminal connection is on the side of the fan near one of the corners. You can get an idea if you go here http://www.sunon.com.tw/products/pdf/ac ... ac-fan.pdf and go to the 120mmx38 fans and look at the mechanical drawing. you can see where the cable comes off. The connectors seem to be an industry standard so all the fan cables allied lists work. I would try it without stacking the fans first and see if that works before you got to all the extra work. If you do stack them you might also try putting the fans on either side of the radiator, that way the radiator will straighten out the airflow for the downstream fan so it works efficiently and you won't need the plenum in there. I would get the straight connectors btw, they give you the most low profile connection and so the most options for mounting.

Allied sell a 1000 ohm 3Watt potentiometer for $5 (EUP1400 1K, Stock number 522-0049) that you can put in series with the 2123XST fan to allow you to control the fan speed down to almost the subaudible range. You will need 1 pot per fan, Don't stick two fans on one pot or you will exceed the dissipation limits of the pot.
If the 2123XST doesn't provide enough airflow at 120V for your application you can put a 4.7uF Capacitor in series with it. This will boost the voltage across the fan to about 160Vac and speed it up considerably. This is no longer in the silent range though. You can still use the pot in series with it to control the speed if you want, but the minimum fan speed will now be greater. Allied electronics has an appropriate capacitor (stock number 613-0500) for $2.11 . You will need one capacitor for each fan.
The Sunon fans are stock number 997-2123
Fan cords are stock number 609-5642 for a 3' cord straight connector

Regular fan speed controllers (like the 3 speed variety for ceiling fans) will NOT work. They will actually increase the fan speed considerably.
You can use the Lutron continously variable speed controller from Lowe's but you need to put a 4.7uf Cap in series (see cap mentioned above) with it to keep it stable throughout it's range. Most triac dimmer/speed controllers go bonkers when you put such an incredibly inductive load on them like this fan. The Lutron controller does impart a little bit of 120Hz switching noise out of the fan but it's pretty low level. Other controllers I've tried are down right raucous if they work at all.
I'm working on a design to allow me to control the AC fans with my T-Balancer, but until then my favored solution is the above mentioned Potentiometer from allied to just set the fan speed and forget it. It's also the quietest solution.
I'm using a Black Ice Pro II 120x2 radiator btw, it's relatively thin (1") and the least restrictive I could find. At the low airflow rates the exhaust temperature of the air is almost as hot as the coolant, so a thicker radiator would not help at all.

bobkoure wrote:

ferdb wrote:

The 2123XST has a terminal connection which you can either solder to or use a connector. Allied sells a number of different fan connector cords

I'm having trouble finding an image of that fan. Where do the connectors attach? In, next to the hub (where I'd sort-of expect). I'm thinking I'd probably need to stack a pair of these (with small plenum between) to get sufficient pressure for a 2" heater core at low noise levels - so this means I'd need the straight connectors, right? I'm also guessing from your post that the fan connector cords are interchangeable. Is that true or is there some particular kind I need to stick to. The Allied catalog assumes I have a background in whatever device I'm buying from them and already have this knowledge.

Re speed control. Any reason why a rheostat wouldn't work? These fans are rated for 22W at 220V - so 1 amp. Any reason why they'd draw more than that at 120V or 90? Or are they non-ohmic devices like processors?Also, I have a couple of speed controllers for 115VAC fans from Edmund. I figure these are at least worth trying. Any reason they'd be a bad idea?

Finally - I'm pretty sure that the real answer to the noise/cooling trade off for 2" heater cores is to not use 2" heater cores. Nick over at Radiator Express has offered to make up a small radiator / heater core to my specs. I'm planning to ask for one that's 6x6x.5 (finned area). Should work nearly as well as the "old standby" - a chevette heater core as it's mostly frontal area that matters. Sorry for being off topic - except that sometimes the answer to a question is to change the question

Is globe's noise, so bad? I mean, can you hear the bearing noise\clicks\whatever (i don't mind air noise) from a distance ~2 feet in a really quiet room? With the fan at 6-7v.

My original application was fans for a radiator on a water cooled setup. I wanted to use 120x38mm fans because thicker fans push air better in restrictive setups like a radiator than the thin fans. I tried every 120x38mm DC fan I could find but they were all annoyingly loud because of the motor/bearing noise they made even at very low speeds. I even tried to modify the coil drive circuits in the fans to make them quieter but met with mixed success.

So I broadened my search to find a good 120x38 fan and eventually found the Sunon 2123XST 230Vac fan. It's surprising how few good 120mm fans are out there, even in the 120x25 category. You only have Nexus, Globe, and the overly expensive Silenx (Adda) for 120mm DC fans. For the average user the 120mm Nexus is without a doubt the fan of choice, it has the best airflow to noise ratio.

I thought there was some real potential in the AC fans so I've been fooling around with them. The drawbacks are you need an extra AC cord into your machine and a relay to turn them on with the computer (or you could just leave them on all the time), and they are not so easily thermally speed controlled as the DC fans.

I'm working on the speed control problems and the $5 pot from Allied is the best and cheapest solution for controlling the speed by hand. I'm trying out some ideas to make a speed control circuit for the AC fans that will work with any DC fan control output. I would like to be able to use my T-Balancer controller on the AC fans.

Overkill? probably. If I was a sensible person I would probably just put 2 of the AC fans on one side of my radiator at a fixed speed to aid against backpressure, and speed controlled Nexus fans on the other side and on the exhaust ports of the case. or just use Nexus fans all around.
It's been an interesting investigation at any rate.

Is globe's noise, so bad? I mean, can you hear the bearing noise\clicks\whatever (i don't mind air noise) from a distance ~2 feet in a really quiet room? With the fan at 6-7v.

I'll report on my experience with the Acoustifan flavor.

When I first used the Acoustifan in my Sonata, I wasn't pleased with the results. Too much bearing noise, some slight clicking etc. After much trial & error, I found my way into Nexus and have been happy since.

I'm currently reevaluating my Sonata setup. Since I've run out of Nexus fans and there are no distributors in my country, I decided to give all my 120mm fans another try. So among Noiseblocker SX2Pro, Vantec Stealth, Antec 1.6, Antec 2.0, Acoustifan (aka Globe), the Acoustifan came out on top. I was running all fans at 5V. At any other voltage I'd be willing to ship some more Nexus

comparing with my previous experience, I think cutting out the fan grill and the rubber moulding around the cut made a huge difference in noise. There's still some very faint bearing noise but it's acceptable. The clicking is totally gone. Even though I had previously used the same silicone fan mounts, it seems it requires further buffering against vibrations.

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